Prolonging battery life is a key concern for many industries and consumers today. As used herein, “battery life” refers to how long a battery (or bank of batteries) can power a load on a single charge cycle. In contrast, “lifetime” of a battery refers to the number of charge/discharge cycles of a rechargeable battery until the battery has naturally degraded irreversibly and can no longer hold enough charge to be useful.
A few non-limiting examples of industries affected by limited battery life are automotive, aerospace, marine, and backup power. For instance, electric vehicles have an unappealing limited range due to battery capacity limitations. More motorists would choose electric vehicles if vehicle range was greater and electrical vehicle cost was more competitive with conventional internal combustion engine vehicles. Battery backup power supplies for homes are unpopular due to limited capacity and cost. Instead, many homeowners prefer noisy, fume-emitting, gas-guzzling generators over battery power to endure a blackout. Anglers must carry extra batteries or judiciously limit their trolling motor usage to endure a fishing trip. As a consequence, batteries of battery powered devices frequently must be replaced or recharged, which can be time consuming, or require a generator, or access to utility power, or extra batteries, etc. There are countless other examples where appeal or usefulness is negatively impacted by battery life limitations.
A battery's “capacity” is the amount of electric charge it can deliver measured in relation to a certain stated voltage. Battery capacity may be considered in terms of state of charge. State of charge may be viewed as available capacity expressed as a percentage of a benchmark reference, such as the rated capacity of a battery or the current capacity of a battery (i.e. the maximum capacity a battery will attain when fully charged at any given point in time). Basing the state of charge on the current capacity of the battery rather than its rated capacity (which only applies when the battery is new) reveals the progressive reduction in capacity over the lifetime of a battery. Either way, a desire is to maintain a battery at a high state of charge for as long as possible before capacity falls below the minimum required to accomplish the task (powering a given load) it has been applied to. In doing so, battery life (i.e. useable capacity) is extended.
Of significance, as the state of charge decreases, voltage decreases. Additionally, the more state of charge decreases, the more rapidly voltage decreases. This is evident in the exemplary state of charge vs. voltage curve for a conventional lead acid battery, as provided in FIG. 1 (labeled as Prior Art since it represents a typical performance curve of a known or conventional lead acid battery). Maintaining a battery in a state of charge above about 60% for as long as possible during discharge will appreciably increase the utility of the battery by avoiding or postponing the most extreme decline in voltage. Below a certain voltage, the battery becomes useless because it is unable to efficiently power a motor, or illuminate a light, or deliver sufficient power for some other load to function. Certain loads, e.g. motors, will operate inefficiently or will not operate at all, and can even be damaged below a minimum voltage. Deep discharging also tends to shorten the lifetime of a battery.
What is needed is a durable, reliable, cost-effective, scalable system that appreciably extends battery life for a wide range of applications, without compromising the lifetime of the battery. Ideally, such a system would extend the lifetime of the battery.
The presently disclosed subject matter is directed to overcoming one or more of the problems and solving one or more of the needs as set forth above.